I would take the style down whenever you don't have to wear it up, constant traction for three days at a time is never going to be good for hair or follicles. TBH I think that is worse that washing a little more often or any rub from your pillow, certainly I wrecked my hair wearing a 24/7 ponytail and I wasn't being as strict as you.

Avoid hairspray and anything with ingredients that build up like silicones or some of the polyquats, try gels/ cream-gels containing oils and/ or humectants, even make your own Ecostyler custard (see YouTube). Some products/ ingredients can be reactivated with just water when you need to tame flyaways. You could then conditioner only wash which would make washing less damaging and for many of us makes our hair less poufy/ frizzy and more manageable. Maybe switch to a Tangle Teezer brush instead of harsh bristles.

Consider different types of buns, different placements or different tools for of securing the hair if permitted - this will mean your hair is not stressed in the same place over and over again. Hair scroos/ spin pins are invisible and you need far fewer to get a secure result than you do with regular grips, bun nets again if allowed. The Long Hair Community has loads of ideas for gentler but secure up dos, and I am sure there have been threads from ladies in the forces.

You might also want to try some hydrolysed protein treatments followed by a deep condition - coconut oil is the best absorbed of all the oils, avocado is also good. My dry/ damaged/ porous hair is liking the combination of an oil and a sugar syrup (some use honey, both are humectants).